Integrated circuits (ICs) often require a constant current source (e.g., a current reference) that is both accurate and stable with respect to temperature and variations in manufacturing process. In some cases, constant current sources are implemented using a level shift stage between a feedback amplifier and a bandgap reference (BGR) voltage source in order to increase the temperature operating range. Additionally, these constant current sources may be implemented with a transistor, such as a n-channel metal oxide semiconductor (NMOS) transistor, that is configured to operate as a resistor that compensates for changes in temperature.